Gastric mucosal cells from the intact mouse stomach and isolated and separated into various cell types will be studied by electron microscopy and histochemistry, as well as by some biochemical and immunological parameters. The cellular localization of carbonic anhydrase in the gastric mucosa and in isolated cells be studied in conjunction with the biochemical demonstration of this enzyme and its immunolabeline pattern. Studies on the structural aspects of gastric mucus release by selective secretagogues will be made in the rat gastric mucosa. In particular agents that are indicative of being protective towards ulcerating agents will be tested and its effect illucidated.